Abstract

Friday, October 23, 2015

A century of centenarians?

When I
was in elementary school, my parents bought three sets of encyclopedias: Encyclopedia Britannica; the junior
version of Encyclopedia Britannica
for my brother and me; and Compton’s,
which had recently been acquired by Encyclopedia Britannica. My recollection is
that, on account of our being such avid consumers of knowledge, we also
received a free collection of forward-looking essays. The first of these
articles posed the question: Will You Live to 100? I already knew that such a
thing was possible. I had a great-grandfather who was in his mid-nineties and,
along with his somewhat younger wife, still grew vegetables on their land. Not
until his late nineties did his mind begin to slacken.

I was thinking of my great-grandparents while attending this
year’s Simons Research Symposium on Alzheimer’s Disease in Waltham last week.
The event’s primary speaker, Dr. Claudia Kawas, a researcher at the University
of California-Irvine, discussed some eye-opening trend lines. In 1961, the year
I was born, life expectancy in the United States was just over seventy,
according to World Bank data.

Kawas noted that children being born in the United States this
year are projected to live to an average age of 103. This is, for lack of a
better word, staggering. Of course, today’s infants are not expected to reach
this projected median age until the second decade of the twenty-second century,
when almost all of us will be gone. It’s easy to imagine a hot, crowded planet
with terrible unemployment and extraordinary suffering—something like the
vision laid out in the 1973 movie Soylent
Green.

Kawas’s interest, of course, is in the here and now. She
has long been involved with the “90-plus study” in Orange County, Calif., which
got underway in 2003. The study’s roots, however, reach back to 1981. That was when
researchers launched the initial Leisure World Cohort Study, named after a vast
Orange County retirement community. The rate of participation in the survey among
Leisure World residents was extremely high—more than three-fourths of the retirement
community’s 18,000 residents took part. And there have been follow-up surveys in
the decades since.

“We didn’t just want to know how long people lived,” Kawas
said. “All of us, we want to live well.”

Some of the recent findings among people in their nineties
were surprising. In terms of health and nutrition, neither Vitamin A, Vitamin C,
nor Vitamin E appear to have much, if any, impact on longevity. And people who
drink moderate amounts of alcohol, be it red wine or beer or Scotch, appear to
live longer on average than those who don’t drink. Moderate consumption of
caffeinated beverages also appears to boost longevity, but the benefit,
according to Kawas, is the same whether it is coffee, black tea or green tea.

Another of the study’s observations is that, in old age,
it is better to be moderately overweight than skinny. Throughout much of human
history, and as recently as the Victorian era, only the well-to-do were likely
to achieve the status of being overweight, though there were exceptions. When
nineteenth-century anthropologists encountered the coastal peoples in the Pacific
Northwest, they were surprised to find tribal members with pot bellies, thanks
to the enormous amounts of salmon and other protein-rich seafood available.

But, of course, the longer one lives, the likelier one is
to develop dementia, which Kawas defined as “the loss of mental abilities
severe enough to interfere with your vocational or social functioning.”

Among people in their early nineties, there is a doubling
of the risk of dementia, from 5 percent to 10 percent; for people in their late
nineties, the risk is 20 percent; and at age 100, the odds are 40 percent.

Kawas’s conclusion: By the middle of this century, there
will be more people in the United States with dementia over the age of 100 than
among all younger people combined.